This invention concerns hydraulic or pneumatic control circuits and valve arrangements that automatically and remotely open and close hydraulically or pneumatically operated fluid control valves located within an irrigation or other fluid distribution system.
An example of such a circuit is an irrigation system which employs control valves that are opened by the venting of pressurized fluid contents that normally cause their closure. Closing the venting pathway permits the reestablishment of pressure, and subsequent closing of the control valves. The source of fluid pressure for this closure may be the irrigation fluid supply itself, or some external source.
Such fluid circuits have previously been used in irrigation systems to control flow of water to soil being monitored for moisture content. U.S. Pat. Nos. 2,743,552; 3,747,399; and 4,055,200, for example, disclose automatic irrigation devices in which a fluid circuit valve is responsive to a ceramic cell which absorbs water from monitored soil surrounding the cell.
Such devices, however, do not always reliably respond to changing moisture conditions in the soil. They therefore do not accurately determine when to initiate irrigation, or how much irrigation water to provide once irrigation is initiated.
It is accordingly a primary object of the invention to provide a fluid control circuit which reliably and consistently detects the amount of fluid in an environment and provides a signal that initiates fluid flow.
It is a further primary object of the invention to provide an irrigation control circuit which accurately monitors the amount of moisture in an environment, and terminates irrigation at a preselected point once sufficient moisture has been provided to the environment.
Another object is to provide such a circuit which responds automatically to changing environmental moisture conditions without the necessity of manual operations.
Yet another object is to provide such a circuit which can be conveniently and selectively activated by an operator.
Another object is to provide such a circuit which can operate solely in response to changing pressure conditions within the circuit.
Another object is to provide a novel fluid control device that effects the automatic activation and deactivation of hydraulically or pneumatically operated fluid control valves in response to differentials in fluid pressure.
In particular, it is an object to provide a control device that is highly sensitive to small and often minute differentials in fluid pressure.
Another object is to provide a control device that opens and closes rapidly and completely upon attainment of desired activating and de-activating differentials in fluid pressure.
A further object is to provide a control device having adjustable, definable and highly repeatable activation and deactivation points.
Also an object is to provide a control device having activation and deactivation points that are largely insensitive to changes in fluid supply pressure.
Yet another object is to provide a fluid control circuit that maintains continuous prime.
Another specific object is to provide an irrigation or fluid control device that can remotely and automatically activate and deactivate a hydraulically or pneumatically operated irrigation or fluid control valve in response to differentials in fluid pressure that result from the drying and wetting of irrigated media, the evaporation and precipitation of fluids, or the draining and replenishment of fluid-containing vessels.
A final specific object is to provide such a device that is responsive to pressure changes or differentials that occur in a piped irrigation or fluid application system during the course of a normal cycle of operation.